B.Satyanarayana, Department of High Energy Physics.

B.Satyanarayana, Department of High Energy Physics

Introduction The INO Iron Calorimeter (ICAL) Principle of operation of RPC Review of RPC detector developments Design and studies of small RPC prototypes Development of RPC materials and procedures Large area RPC development Construction of ICAL prototype detector Data analysis and results Summary and future outlook Acknowledgements 2B.Satyanarayana, DHEP November 5, 2008

RPC R&D was motivated by its choice for INOs neutrino experiment. B.Satyanarayana, DHEP November 5, 20083

Proposed by Wolfgang Pauli in 1930 to explain beta decay. Named by Enrico Fermi in 1931. Discovered by F.Reines and C.L.Cowan in 1956. Created during the Big Bang, Supernova, in the Sun, from cosmic rays, in nuclear reactors, in particle accelerators etc. Interactions involving neutrinos are mediated by the weak force. B.Satyanarayana, DHEP November 5, 20084

5 < 2.2eV < 170keV

Atmospheric neutrino energy > 1.3GeV m 2 ~2-3 10 -3 eV 2 Downward muon neutrino are not affected by oscillation They may constitute a near reference source Upward neutrino are instead affected by oscillation since the L/E ratio ranges up to 4 Km/GeV They may constitute a far source Thus, oscillation studies with a single detector and two sources B.Satyanarayana, DHEP November 5, 20089

Matter effects help to cleanly determine the sign of the m 2 Neutrinos and anti- neutrinos interact differently with matter ICAL can distinguish this by detecting charge of the produced muons, due to its magnetic field Helps in model building for neutrino oscillations B.Satyanarayana, DHEP November 5, 200810

Source of neutrinos Use atmospheric neutrinos as source Need to cover a large L/E range Large L range Large E range Physics driven detector requirements Should have large target mass (50-100 kT) Good tracking and energy resolution (tracking calorimeter) Good directionality (< 1 nSec time resolution) Charge identification capability (magnetic field) Modularity and ease of construction Compliment capabilities of existing and proposed detectors Use magnetised iron as target mass and RPC as active detector medium B.Satyanarayana, DHEP November 5, 200811

B.Satyanarayana, DHEP November 5, 200812 INO Peak (2203m) Singara, about 105km south of Mysore or about 35km north of Ooty. About 6km from the TNEBs PUSHEP established township in Masinagudi. The INO cavern will be built at about 2.3 km from the INO under ground tunnel portal. 7,100km from CERN, Geneva Magic baseline distance! Wealth of information on the site, geology,seismicity, and rock quality etc. Singara, about 105km south of Mysore or about 35km north of Ooty. About 6km from the TNEBs PUSHEP established township in Masinagudi. The INO cavern will be built at about 2.3 km from the INO under ground tunnel portal. 7,100km from CERN, Geneva Magic baseline distance! Wealth of information on the site, geology,seismicity, and rock quality etc.

B.Satyanarayana, DHEP November 5, 200813 4000m m 2000mm 56mm low carbon iron slab RPC 16m 16m 14.5m

Gaseous detector of planar geometry, high resistive electrodes, wire-less signal pickup B.Satyanarayana, DHEP November 5, 200814

B.Satyanarayana, DHEP November 5, 200815 3

Electron-ion pairs produced in the ionisation process drift in the opposite directions. All primary electron clusters drift towards the anode plate with velocity v and simultaneously originate avalanches A cluster is eliminated as soon as it reaches the anode plate The charge induced on the pickup strips is q = (-ex e + ex I )/g The induced current due to a single pair is i = dq/dt = e(v + V)/g ev/g, V v Prompt charge in RPC is dominated by the electron drift B.Satyanarayana, DHEP November 5, 200816

Let, n 0 = No. of electrons in a cluster = Townsend coefficient (No. of ionisations/unit length) = Attachment coefficient (No. of electrons captured by the gas/unit length) Then, the no. of electrons reaching the anode, n = n 0 e ( - )x Where x = Distance between anode and the point where the cluster is produced. Gain of the detector, M = n / n 0 Let, n 0 = No. of electrons in a cluster = Townsend coefficient (No. of ionisations/unit length) = Attachment coefficient (No. of electrons captured by the gas/unit length) Then, the no. of electrons reaching the anode, n = n 0 e ( - )x Where x = Distance between anode and the point where the cluster is produced. Gain of the detector, M = n / n 0 B.Satyanarayana, DHEP November 5, 200817 A planar detector with resistive electrodes Set of independent discharge cells Expression for the capacitance of a planar condenser Area of such cells is proportional to the total average charge, Q that is produced in the gas gap. Where, d = gap thickness V = Applied voltage 0 = Dielectric constant of the gas Lower the Q; lower the area of the cell (that is dead during a hit) and hence higher the rate handling capability of the RPC A planar detector with resistive electrodes Set of independent discharge cells Expression for the capacitance of a planar condenser Area of such cells is proportional to the total average charge, Q that is produced in the gas gap. Where, d = gap thickness V = Applied voltage 0 = Dielectric constant of the gas Lower the Q; lower the area of the cell (that is dead during a hit) and hence higher the rate handling capability of the RPC

Role of RPC gases in avalanche control Argon is the ionising gas R134a to capture free electrons and localise avalanche e - + X X - + h (Electron attachment) X + + e - X + h (Recombination) Isobutane to stop photon induced streamers SF 6 for preventing streamer transitions Growth of the avalanche is governed by dN/dx = N The space charge produced by the avalanche shields (at about x = 20) the applied field and avoids exponential divergence Townsend equation should be dN/dx = (E)N Role of RPC gases in avalanche control Argon is the ionising gas R134a to capture free electrons and localise avalanche e - + X X - + h (Electron attachment) X + + e - X + h (Recombination) Isobutane to stop photon induced streamers SF 6 for preventing streamer transitions Growth of the avalanche is governed by dN/dx = N The space charge produced by the avalanche shields (at about x = 20) the applied field and avoids exponential divergence Townsend equation should be dN/dx = (E)N B.Satyanarayana, DHEP November 5, 200818

B.Satyanarayana, DHEP November 5, 200819 Gain of the detector 10 8 Charge developed ~ 100pC No need for a preamplier Relatively shorter life Typical gas mixture Fr:iB:Ar::62.8:30 High purity of gases Low counting rate capability Avalanche modeStreamer mode

B.Satyanarayana, DHEP November 5, 200820 Glass RPCs have a distinctive and readily understandable current versus voltage relationship.

No. of clusters in a distance g follows Poisson distribution with an average of Probability to have n clusters Intrinsic efficiency max depends only on gas and gap Intrinsic time resolution t doesnt depend on the threshold B.Satyanarayana, DHEP November 5, 200821 Gas: 96.7/3/0.3 Electrode thickness: 2mm Gas gap: 2mm Relative permittivity: 10 Mean free path: 0.104mm Avg. no. of electrons/cluster: 2.8 Charge threshold: 0.1pC HV: 10.0KV Townsend coefficient: 13.3/mm Attachment coefficient: 3.5/mm Efficiency: 90% Time resolution: 950pS Total charge: 200pC Induced charge: 6pC

Creativity aided by intrinsic tunability of the RPC device B.Satyanarayana, DHEP November 5, 200822

B.Satyanarayana, DHEP November 5, 2008 24 Multi gap RPC Double gap RPC Micro RPCHybrid RPC Single gap RPC

ExperimentCoverage(m 2 )ElectrodesGap(mm)GapsMode BaBar2000Bakelite21Streamer Belle2000Glass22Streamer ALICE Muon72Bakelite21Streamer ATLAS7000Bakelite21Avalanche CMS6000Bakelite22Avalanche STAR60Glass0.225Avalanche ALICE TOF160Glass0.2510Avalanche OPERA3000Bakelite21Streamer YBJ-ARGO5600Bakelite21Streamer BESIII1500Bakelite21Streamer HARP10Glass0.34Avalanche B.Satyanarayana, DHEP November 5, 200825 Also deployed in COVER_PLASTEX,EAS-TOP, L3 experiments

The first RPC built at TIFR was 30cm 10cm! B.Satyanarayana, DHEP November 5, 200826

B.Satyanarayana, DHEP November 5, 200827

Two RPCs of 40cm 30cm in size were built using 2mm glass for electrodes Readout by a common G-10 based signal pickup panel sandwiched between the RPCs Operated in avalanche mode (R134a: 95.5% and the rest Isobutane) at a high voltage of 9.3KV Round the clock monitoring of RPC and ambient parameters temperature, relative humidity and barometric pressure Were under continuous operation for more than three years Chamber currents, noise rate, combined efficiencies etc. were stable Long-term stability of RPCs is thus established B.Satyanarayana, DHEP November 5, 200829 Relative humidity Pressure Temperature

Continuous interaction with local industry and quality control standards B.Satyanarayana, DHEP November 5, 200830

B.Satyanarayana, DHEP November 5, 2008 31 Edge spacer Gas nozzle Glass spacer Schematic of an assembled gas volume

Graphite paint prepared using colloidal grade graphite powder(3.4gm), lacquer(25gm) and thinner(40ml) Sprayed on the glass electrodes using an automobile spray gun. A uniform and stable graphite coat of desired surface resistivity (1M / ) was obtained by this method. B.Satyanarayana, DHEP November 5, 200832

B.Satyanarayana, DHEP November 5, 200833 Glass holding tray Automatic spray gun Drive for Y-movement Drive for X-movement Control and drive panel

B.Satyanarayana, DHEP November 5, 2008 34 On films On glass

B.Satyanarayana, DHEP November 5, 2008 36 F ront view Internal view Rear view

B.Satyanarayana, DHEP November 5, 2008 37 Open10051 48.2 47 Honeycomb panel G-10 panel Foam panel Z 0 : Inject a pulse into the strip; tune the terminating resistance at the far end, until its reflection disappears.

Scaling up dimensions without deterioration of characteristics B.Satyanarayana, DHEP November 5, 200838

B.Satyanarayana, DHEP November 5, 200839 1m 1m

Want to check if everything works as per design! B.Satyanarayana, DHEP November 5, 200841

B.Satyanarayana, DHEP November 5, 200842 13 layer sandwich of 50mm thick low carbon iron (Tata A-grade) plates (35ton absorber) Detector is magnetised to 1.5Tesla, enabling momentum measurement of 1-10Gev muons produced by interactions in the detector.

B.Satyanarayana, DHEP November 5, 2008 200 boards of 13 types Custom designed using FPGA,CPLD,HMC,FIFO,SMD

Using a ROOT based package BigStackV3.8 B.Satyanarayana, DHEP November 5, 200845

B.Satyanarayana, DHEP November 5, 200848 Temperature

B.Satyanarayana, DHEP November 5, 2008 49 Temperature R.H Current

RPC: Is it the best thing happened after MWPC? B.Satyanarayana, DHEP November 5, 200850

Large detector area coverage, thin (~10mm), small mass thickness Flexible detector and readout geometry designs Solution for tracking, calorimeter, muon detectors Trigger, timing and special purpose design versions Built from simple/common materials; low fabrication cost Ease of construction and operation Highly suitable for industrial production Detector bias and signal pickup isolation Simple signal pickup and front-end electronics; digital information acquisition High single particle efficiency (>95%) and time resolution (~1nSec) Particle tracking capability; 2-dimensional readout from the same chamber Scalable rate capability (Low to very high); Cosmic ray to collider detectors Good reliability, long term stability Under laying Physics mostly understood! B.Satyanarayana, DHEP November 5, 200851

Starting from modest 30cm 30cm chambers Now, 100cm 100cm RPCs are being routinely fabricated and characterised in detail Long-term stability of these chambers is established ICAL prototype detector is being assembled Almost all the required materials and procedures designed and optimised for production Fabrication and testing of 200cm 200cm RPCs to start soon Detailed studies using the prototype detector stack will continue Design and optimisation of gas recirculation system B.Satyanarayana, DHEP November 5, 200852

Incorporating and optimisation of ICAL specific parameters and constraints in the production designs Large scale production of RPCs is being thought about Parallel production of chambers at multiple assembly centres with common quality control standards B.Satyanarayana, DHEP November 5, 200853

Growth is necessarily built around people B.Satyanarayana, DHEP November 5, 200854

Anita Behere, M.S.Bhatia, V.B.Chandratre, V.M.Datar, M.D.Ghodgaonkar, S.K.Mohammed, S.K.Kataria, P.K.Mukhopadhyay, S.M.Raut, R.S.Shastrakar, Vaishali Shedam Bhabha Atomic Research Centre, Mumbai Amitava Raychaudhuri Harish-Chandra Research Institute, Allahabad Satyajit Jena, Basanta Nandi, S.Uma Sankar, Raghava Varma Indian Institute of Technology Bombay, Mumbai D.Indumathi, M.V.N.Murthy, G.Rajasekaran, D.Ramakrishna Institute of Mathematical Sciences, Chennai Y.P.Viyogi Institute of Physics, Bhubaneswar Sudeb Bhattacharya, Suvendu Bose, Satyajit Saha, Manoj Saran, Sandip Sarkar, Swapan Sen Saha Institute of Nuclear Physics, Kolkata B.S.Acharya, V.V.Asgolkar, Sarika Bhide, Manas Bhuyan, Santosh Chavan, Amol Dighe, M.Elangovan, G.K.Ghodke, P.R.Joseph, V.S.Jeeva, S.R.Joshi, S.D.Kalmani, Darshana Koli, Shekhar Lahamge, Vidhya Lotankar, G.Majumder, N.K.Mondal, P.Nagaraj, B.K.Nagesh, G.K.Padmashree, Subhendu Rakshit, K.V.Ramakrishnan, Shobha Rao, L.V.Reddy, Asmita Redij, Deepak Samuel, Mandar Saraf, S.B.Shetye, R.R.Shinde, Noopur Srivastava, S.Upadhya, Piyush Verma, Central Services, Central Workshop, Visiting Students Tata Institute of Fundamental Research, Mumbai Saikat Biswas, Subhasish Chattopadhyay Variable Energy Cyclotron Centre, Kolkata UICT, Mumbai & Local Industries

Ian Crotty, Christian Lippmann, Archana Sharma, Igor Smirnov, Rob Veenhof CERN, Switzerland Adam Para, Makeev Valeri Fermilab, USA Carlo Gustavino, M.C.S.Williams INFN, Italy Kazuo Abe, Daniel Marlow Belle Experiment, Japan Jianxin Cai Peking University, China Rinaldo Santonico University of Roma, Italy

For further information INO homepage: http://www.imsc.res.in/~ino TIFR INO homepage: http://www.ino.tifr.res.in My INO homepage: http://www.hecr.tifr.res.in/~bsn/ino

B.Satyanarayana, Department of High Energy Physics.

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